The present invention relates to a base catalyst and to a method for producing a derivative of carbonyl compound using the same. More particularly, the present invention relates to a base catalyst comprising an alkali metal compound selected from the group consisting of alkoxides, hydroxides and oxides of alkali metals and an alkaline-earth metal oxide, and to a method for producing a derivative of carbonyl compound, such as glycol monoesters or the like, from aldehydes using the catalyst.
Base catalysts are used in synthetic reactions, such as aldol condensation reaction, for producing many kinds of compounds. When reactions are conducted on an industrial scale using base catalysts, there have been widely used alkali metal hydroxides, typically sodium hydroxide, and alkali metal alkoxides, typically sodium methoxide.
However, most of the alkali metal hydroxides and alkoxides act as a homogeneous catalyst in the reaction system and, hence, they require neutralization and washing with water as operations for removing the catalyst after completion of the reaction. This naturally results in the production of a large amount of waste water. In general, homogeneous catalysts produce larger amounts of by-products, so that it is often the case that a selectivity of the product (selectivity of the target product) is lowered.
On the other hand, in Japanese Patent Application Laid-open No 58-65245, a method in which an alkaline-earth metal oxide is used as a solid base catalyst in a method for producing a glycol monoester from an aldehyde with a solid base catalyst is described. However, reactions with barium oxide or magnesium oxide alone, for example, could afford low levels of catalytic activity so that it has been difficult to provide sufficient catalytic activity by using alkaline-earth metal oxides alone.
As described above, with conventional catalyst systems, use of homogeneous catalysts having higher activity has caused a larger amount of waste water whereas use of heterogeneous catalysts has caused only a small amount of waste water, but it has made it difficult to obtain sufficient catalyst activity or product selectivity.
Generally, use of heterogeneous solid catalysts, as compared to homogeneous catalyst reactions, provides the following advantages.
(1) There is no need for such operations as neutralization, washing with water, or the like of the catalyst, resulting in the production of no or much less waste water.
(2) The catalyst can be reused.
(3) Product selectivity is high in most cases.
Therefore, it can be expected that methods which involve use of heterogeneous solid catalysts are simpler in process, less inexpensive in cost for a plant, and higher in yield of the target product as compared with those methods using homogeneous catalysts to obtain the target products. Further, because of generating no or much less waste water as compared with the latter methods using homogeneous catalysts, the former methods not only yield less cost for disposal of waste water but also enable suppression of adverse effects on environment, of which a problem has been arisen recently.
However, as stated above, none of the conventional heterogeneous solid catalysts could present sufficient catalytic activity nor sufficient product selectivity and, hence, a further technical innovation has been needed.
It is an object of the present invention to solve the above-described problems and provide an efficient base catalyst which can be applied to base catalyst reactions generally employed, for example, aldol reaction, Michael addition reaction, Tishchenko reaction and the like and which can produce a target product at high activity and high selectivity.
Previously, the present inventors completed an invention on a method for producing carbonyl compound derivatives using a solid base catalyst comprising barium and calcium (Japanese Patent Application Laid-open No 8-29979) and their further study revealed that use of an alkaline-earth metal oxide which is a conventional solid base catalyst, in combination with a minute amount of an alkali metal compound as catalysts and of a two-step reaction with employing the alkali metal compound as a catalyst in the earlier reaction step and the alkaline-earth metal oxide in the later reaction step increases the catalytic activity, which allows a remarkable decrease in the amount of the catalyst to be used, and an increase in product selectivity, and suppresses generation of waste water to a minimum level, thus completing the present invention.
That is, the base catalyst of the present invention comprises at least one alkali metal compound selected from the group consisting of alkoxides, hydroxides and oxides of alkali metals and an alkaline-earth metal oxide with a weight ratio of the alkali metal compound to the alkaline-earth metal oxide, which is calculated by a formula, xe2x80x9cthe weight of alkaline metal compound/the weight of alkaline-earth metal oxidexe2x80x9d, being from 0.005 to 1.
The method for producing a derivative of carbonyl compound according to the present invention is a method for producing a derivative of carbonyl compound from a carbonyl compound in the presence of a catalyst wherein the catalyst is a catalyst comprising at least one alkali metal compound selected from the group consisting of alkoxides, hydroxides and oxides of alkali metals and an alkaline-earth metal oxide.
Another method for producing a derivative of carbonyl compound according to the present invention comprises an earlier reaction step in which at least one alkali metal compound selected from the group consisting of alkoxides, hydroxides and oxides of alkali metals is used as the catalyst, and a later reaction step in which an alkaline-earth metal oxide is used as the catalyst.
When the reaction is carried out with an alkali metal compound alone as a catalyst, high catalytic activity is obtained while product selectivity is insufficient. In contrast, use of an alkaline-earth metal oxide alone results in a decreased reactivity. The base catalyst of the present invention is a base catalyst which comprises an alkali metal compound and an alkaline-earth metal oxide in combination in a specified weight ratio, can provide high catalytic activity and excellent product selectivity simultaneously and generates less waste water.
Hereafter, embodiments of the present invention will be described.
(1) Base Catalyst
The base catalyst of the present invention comprises an alkali metal compound and an alkaline-earth metal oxide.
The alkali metal compound of the present invention is selected from the group consisting of alkali metal alkoxides, alkali metal hydroxides and alkali metal oxides. The alkali metals include preferably sodium, potassium and lithium but are not limited thereto.
As the alkali metal alkoxides, there can be used those whose alkyl group contains 1 to 12 carbon atoms. Specific examples thereof include sodium methoxide, sodium ethoxide, sodium t-butoxide, potassium methoxide, potassium ethoxide, potassium t-butoxide, lithium methoxide, lithium ethoxide, lithium t-butoxide, etc.
As the alkali metal hydroxides, there can be used, preferably sodium hydroxide, potassium hydroxide, lithium hydroxide, etc. And as the alkali metal oxides, there can be used preferably sodium oxide, potassium oxide, lithium oxide, etc.
The alkaline-earth metals in the alkaline-earth metal oxides of the present invention include magnesium, calcium, barium and strontium, preferably calcium, barium and strontium, particularly preferably barium and strontium, but are not limited thereto. Specific examples of the alkaline-earth metal oxides include calcium oxide, barium oxide and strontium oxide.
The weight ratio of the alkali metal compound to the alkaline-earth metal oxide in the base catalyst of the present invention is such that alkali metal compound/alkaline-earth metal oxide=0.005 to 1, preferably, 0.01 to 0.5 (weight ratio). When this ratio is too small, the catalytic activity of the base catalyst as a whole tends to become low, whereas when it is too large, the product selectivity tends to decrease.
The alkali metal compounds used in the present invention may be in any form, such as powder, particle, mass, liquid, and the like. And the alkaline-earth metal oxide used in the present invention may be in any form, such as powder, particle, mass, and the like. Among the forms, preferred one is a combination of a liquid alkali metal compound and a solid alkaline-earth metal oxide.
The base catalyst of the present invention, containing a combination of a solid alkaline-earth metal oxide and an alkali metal compound which acts in the form of a liquid in the reaction system in appropriate amounts, can overcome high cost and low catalytic activity which are disadvantages of the alkaline-earth metal oxides, and also can suppress to a minimum level the generation of a large amount of waste water accompanying neutralization and washing with water and overcome the low selectivity of target compound which are disadvantages of the alkali metal compounds.
As the alkali metal compounds and alkaline-earth metal oxides, i.e., the components of the base catalyst of the present invention, there can be used commercially available ones as they are. Further, as for the method for preparing the base catalyst, there can be used known methods, for example, a method in which an alkali metal compound and an alkaline-earth metal oxide are mixed by a known means.
Since it comprises the alkali metal compound and alkaline-earth metal oxide, the base catalyst of the present invention may be used in any form of use as far as the both are employed in combination. For example, the alkali metal compound and alkaline-earth metal oxide may be simultaneously or previously mixed and formulated so that they can be added in the lump to the reaction system. Alternatively, the components of the catalyst may be used in two steps separately, in such a manner that the reaction is carried out using the alkali metal compound at the first step and using the alkaline-earth metal oxide at the second step.
While the base catalyst of the present invention can be used in general base catalyst reactions, it can be used advantageously in producing preferably derivatives of carbonyl compound from carbonyl compounds. In particular, it exhibits considerable effects when used in producing 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate from isobutyraldehyde but the present invention is not limited thereto.
(2) Production Method of Carbonyl Compound Derivatives
The production method of the present invention is to produce a derivative of carbonyl compound from a carbonyl compound in the presence of a catalyst which comprises an alkali metal compound and an alkaline-earth metal oxide. The alkali metal compound and the alkaline-earth metal oxide which are used may be those employed in the base catalyst described above. The weight ratio of the alkali metal compound and the alkaline-earth metal oxide in the above-described catalyst is not limited particularly but the above-described base catalyst wherein the weight ratio of them is such that alkali metal compound/alkaline-earth metal oxide=0.005 to 1, more preferably 0.01 to 0.5 (weight ratio) is used preferably.
The carbonyl compounds used as starting materials in the production method of the present invention are not limited particularly as far as they are organic compounds having a carbonyl group and include, for example, aldehydes and ketones, preferably aldehydes, more preferably aldehydes having 2 to 12 carbon atoms, particularly preferably aliphatic aldehydes having 4 to 8 carbon atoms. More specifically, the aliphatic aldehydes include isobutyraldehyde, n-butyraldehyde, 2-ethylbutyraldehyde, 2-ethylhexylaldehyde, and the like. As the ketone, there can be cited acetone. However, the present invention is not limited to these compounds.
As the method for producing the carbonyl compound derivatives from carbonyl compounds according to the present invention, there can be cited those that involve reactions which can proceed on the carbonyl compounds as starting compounds, in the presence of base catalysts, such as aldol condensation reaction, Tishchenko reaction, Michael addition reaction, and the like.
For example, there can be cited a method for producing glycol monoesters from aldehydes, a method for producing xcex2-hydroxy aldehydes or xcex1,xcex2-unsaturated aldehydes from aldehydes, or the like. Therefore, the carbonyl compound derivatives produced by the method of the present invention can include glycol monoesters, xcex2-hydroxy aldehydes, xcex1,xcex2-unsaturated aldehydes, and the like, which are produced from carbonyl compounds by the above-described reactions.
More preferred one is a method for producing glycol monoesters represented by general formula (II) from aldehydes represented by general formula (I): 
wherein, R1 and R2 in formula (I), which may be same or different, independently represent an alkyl group having 1 to 5 carbon atoms, preferably 1 to 3 carbon atoms; 
wherein, R1, and R2 in formula (II) have the same meanings as defined in formula (I).
The method of the present invention is highly effective particularly in the method of producing 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate as a carbonyl compound derivative from isobutyraldehyde as a carbonyl compound (in formulae (I) and (II) above, R1, and R2 are each a methyl group) but the present invention is not limited thereto.
The carbonyl compound as a starting material is preferably those which contain less acid and water which are contained as impurities. However, the carbonyl compound with an acid content of 0.1% by weight or less and a water content of 0.1% by weight or less may be well used in the present invention.
The production method of the present invention may be carried out either as a continuous process or as a batch process. Usually, the reaction is carried out preferably under inert atmosphere such as nitrogen and the like in a reaction vessel equipped with a stirrer.
As the method of addition of the base catalyst to the reaction system, there can be cited a method in which the alkali metal compound and alkaline-earth metal oxide are added in the lump and stirred together with the carbonyl compound as a starting material to proceed the reaction in one step, for example, simultaneous incorporation of the alkali metal compound and the alkaline-earth metal oxide in the reaction vessel or mixing and preparing them in advance before they can be incorporated into the reaction vessel.
It is also possible to adopt a 2-step addition method in which the alkali metal compound is added first followed by addition of the alkaline-earth metal oxide. That is, the reaction may be divided into two steps, i.e., earlier reaction step and later reaction step, with using as a catalyst the alkali metal compound in the earlier reaction step and the alkaline-earth metal oxide in the later reaction step to complete the reaction.
Accordingly, a preferred production method according to the present invention comprises an earlier reaction step using at least one alkali metal compound selected from the group consisting of alkoxides, hydroxides and oxides of alkali metals as a catalyst and a later reaction step using an alkaline-earth metal oxide as a catalyst. Here, use of the alkaline-earth metal oxide in the earlier reaction step and the alkali metal compound in the later reaction step is not preferable since the reactivity tends to decrease.
The method of diving the reaction in two steps and adding different catalysts in different steps separately (hereafter, sometimes referred to as xe2x80x9ctwo-step reaction methodxe2x80x9d) has the following advantages. That is, it is otherwise necessary to add an excess amount of catalyst taking into consideration of deactivation of the catalyst added due to the moisture which the carbonyl compound used as a starting material contains not a little. On the other hand, alkaline-earth metal oxides such as barium oxide and the like are more expensive than alkali metal compounds and therefore there has been a problem that adding the alkaline-earth metal oxides in the reaction system from the beginning results in using them in excess amounts, which is costly. According to the two-step reaction method of the present invention, first an alkali metal compound, which is inexpensive, is added to the reaction system to kill the moisture therewith, and subsequently the alkaline-earth metal oxide is added to run the reaction, so that the amount of using of the expensive alkaline-earth metal oxide can be minimized, which makes the system economically competitive. Since the effects of moisture can be removed reliably and for some reasons, the method of the present invention can provide, with good reproducibility and stably, conversion ratio into the target product and, selectivity and yield for the target product superior to those of the conventional methods.
In the two-step reaction method, the timing at which the alkali metal compound and the alkaline-earth metal oxide are added may be decided appropriately and empirically depending on the kind and water content of carbonyl compound to be used, and so on, but preferably the reaction time for the earlier reaction step using the alkali metal compound lasts 0.1 to 2 hours and that for the later reaction step using the alkaline-earth metal oxide lasts for 0.2 to 3 hours. Therefore, it is preferred to decide the timing of addition of the respective catalyst components such that the respective steps can be run in the above-mentioned reaction times.
The weight ratio of the alkali metal compound and alkaline-earth metal oxide in the two-step reaction method is not limited particularly but is preferably such that alkali metal compound/alkaline-earth metal oxide=0.005 to 1, more preferably 0.01 to 0.5 (weight ratio), as in the above-described one-step reaction.
In the production method of the present invention, for the one-step reaction, it is possible to use a catalyst comprising a combination of an alkali metal compound and an alkaline earth metal oxide in an amount of 0.01 to 20% by weight, preferably 0.05 to 5% by weight, based on the weight of the reaction liquid i.e. the carbonyl compound used as the starting material, but the present invention is not limited thereto.
Further, in the above-described two-step reaction method, it is preferred to use the alkali metal compound within the ranges of 0.001 to 0.1% by weight and the alkaline-earth metal oxide within the ranges of 0.01 to 10% by weight based on the weight of the reaction liquid but the present invention is not limited thereto.
In the production method of the present invention, the reaction temperature at which the above-described catalyst is used is selected from the ranges of preferably 10 to 130xc2x0 C. For example, when the reaction is run in a batch process, a mixture of the catalyst and the reaction liquid is kept at 10 to 130xc2x0 C. for 0.3 to 5 hours. At temperatures below 10xc2x0 C., the reaction rate is insufficient whereas the product selectivity is aggravated at temperatures above 130xc2x0 C.
For the one-step reaction, it is more preferable to select the reaction temperature from the ranges of 40 to 100. For example, when the reaction is carried out in a batch process, a mixture of the catalyst and reaction liquid is kept at 40 to 100xc2x0 C. for 0.3 to 5 hours.
Further, for the two-step reaction method, it is preferred that the earlier reaction step be run at a reaction temperature of 10 to 70xc2x0 C. for 0.1 to 2 hours and the later reaction step be carried out at a reaction temperature of 50 to 100xc2x0 C. for 0.2 to 3 hours.
After the reaction is completed, the target product can be obtained from the reaction mixture, for example, by washing the reaction mixture with a minute amount of water and distilling it by a known method.
Hereafter, examples of the present invention will be described.